@Amir102

Dev Log 7# Finished the cad for the new bigger servo mounts which are angled at 30 deg offset off of each other to save space on the rail assembly

ROBOTIC ARM Finally finished the complete assembly of all the electronics such as the servos in the forearm and the cover ontop of the now integrated electronics and the wires!

Today I completely redesigned the finger of my robotic hand. The flexor tendent now runs along the bottom of the finger opposed to the top according to human anatomy and as such grants a lot more grip strength and fluid motion. the only downside to doing things this way is that I no longer have control over every individual segment decreasing the amount of possible grips. However one thing I noticed when testing the prototype is that the grip is self forming which means the finger will bend only the right segment when grabbing a round or square object. The only thing which I kept from previous versions is the contracting tendons in the form of a bungee cord running along rollers at the top of the finger.

Update on the wrist of my robotic arm. It now uses a gear train to transmit power to the first joint of the wrist instead of pulleys and string which allows for lower backlash and more reliability because the string would usually tear or slip out of the pully

Today I assembled the V2 of the wrist assembly for my robotic arm project . This new wrist has more realistic and human like bounds and constraints for its movement and is much more robust around the second join mount to the wrist. There is still the issue of too much slack in the pulleys which is currently being fixed by implementing gears

Dev Log #2 V2 CAD of my anthropomorphic cable actuated prosthesis now using silicon bungee cords for retraction and more robust braided cable for extension.

Devlog #1 — Cable-Actuated Anthropomorphic Robotic Hand

Date: June 26, 2026
Project: Servo-driven, tendon-actuated robotic hand → future prosthesis R&D

Overview

Kicking off the build log for this one. The long-term goal is a functional prosthetic hand, but right now the focus is proving out the core actuation mechanism: an anthropomorphic hand where the fingers are driven by cables (tendons) rather than having a motor sitting in each joint.
Current State of the Build

Two digits are up and mounted on the wrist and fore arm assembly:

Each finger is a multi-joint, 3D-printed linkagecurrently being actuated and tested independently of a full hand.
Actuation is cable-driven through the clear tubes running down each finger, they’re tendon sheaths. They let a servo mounted remotely (down at the base) pull a cable up into the digit via a pully without the servo’s weight or footprint being in the finger it self. The Servos are wired to a PCA9685 16 channel servo driver and an Arduino Nano for easy wiring , code organization, and power distribution as the 22 servos can realistically draw up to 8 amps from my power supply.

Engineering Notes

The cable-actuation choice is the most important design decision so far. Trade-offs worth tracking as the project matures:

Pros: lighter digits, smaller joint profile, mimics natural tendon-driven motion, easier to pack more DOF into a small finger footprint.
Cons to watch: cable stretch/friction inside the tubing over many cycles, routing complexity as digit count goes up, and the need for some kind of tensioning adjustment per tendon.

Next Steps

Finish the remaining three fingers
Design a palm assembly that properly houses tendon routing and pulley/anchor points
Investigate feedback — flex sensors or load cells on the tendons for grip force sensing
Start scoping the eventual socket/interface and control input